Efficacy of Peroxyacetic Acid Wash against Escherichia coli O157:H7, Listeria monocytogenes and Salmonella on Citrus Fruits

Introduction: All fruit and vegetable juices sold as juice or for use as an ingredient in other beverages are subject to the Juice HACCP regulation. Plant HACCP programs identify the washing process as part of the kill step for citrus juice products. Citrus juice processors may apply single or multiple treatments to fruit surfaces, provided that the 5-log reduction process begins after culling and cleaning, and the reduction is accomplished within a single production facility.

Purpose: The objective of this study was to determine the antimicrobial efficacy of peroxyacetic acid (PAA) wash against Escherichia coli O157:H7, Listeria monocytogenes and Salmonella on citrus fruits.

Methods: Oranges, lemons, limes and grapefruits were surface inoculated with E. coli O157:H7, L. monocytogenes and Salmonella. Inoculated samples were washed with 13.6 ppm or 80 ppm PAA for 5 min.

Results: Variations among the citrus fruits and test pathogens were observed. The 13.6 ppm PAA treatment for 5 min was effective in reducing counts of E. coli O157:H7, Salmonella and L. monocytogenes on oranges by 4.75 log, 3.96 log and 5.03 log, respectively. The populations of E. coli O157:H7, Salmonella and L. monocytogenes were reduced, on average, by 3.69 log, 4.44 log and 3.81 log, respectively, on lemons, limes and grapefruits when treated with the 80 ppm solution of PAA for 5 min. 

Significance: The experimental test results showed that the 80 ppm PAA treatment for 5 min in combination with an additional surface treatment that delivers 1.5 to 2-log reduction of E. coli O157:H7, Salmonella and L. monocytogenes on oranges, lemons, limes and grapefruits will achieve the 5-log pathogen reduction performance standard. Alternatively, the 80 ppm PAA treatment for longer than 5 min may deliver the required 5-log reduction on citrus fruits.